The present invention relates generally to the field of automatic transmission hydraulic systems and, more particularly, to an improved pump shaft for the Ford AX4S, AXODE, and AXOD transaxles and other similar transmissions.
The Ford AX4S transaxle has a variable displacement pump that supplies fluid under pressure to the hydraulic system. In the Ford transaxle the torque converter cover assembly drives the impeller blades and rotates a pump drive shaft that operates the pump. It contains hydraulic fluid and provides a mating surface for the Torque Converter Clutch (TCC) piston and damper assembly. The turbine is driven by fluid from the impeller and transmits power to the chain drive and planetary gear sets. The reactor or stator component redirects fluid flow returned from the turbine to the impeller so that it rotates in the same direction as the impeller, which assists in torque multiplication.
The original equipment manufacture (hereinafter “OEM”) pump drive shaft includes fluid passages extending through the shaft and through an internal flow tube installed therein, which transmit automatic transmission fluid (hereinafter “ATF”) to the TCC piston to release the torque converter clutch. The internal ATF flow tube installed within the pump drive shaft defines an axial fluid passage between the flow tube and the pump shaft bore, which forms part of the turbine fluid circuit and carries ATF flow from the torque converter.
A problem in the Ford AX4S transaxle arises when this axial fluid passage becomes even partially restricted with particulate debris upsetting the balance of ATF flow through the torque converter. The lack of adequate ATF flow may cause delayed engagement, converter shudder, overheating, and lock up problems. Thus, the present invention has been developed to resolve this problem and other shortcomings of the prior art.